[runtime] Optimize and unify rest parameters.

src/arm64/code-stubs-arm64.cc

Index: src/arm64/code-stubs-arm64.cc
diff --git a/src/arm64/code-stubs-arm64.cc b/src/arm64/code-stubs-arm64.cc
index e672b9dec8d63c0c4b8ad9b8a66589d961d67dd5..da77ca5d45dd44e2d34b4507d802eb9e4a4fa308 100644
--- a/src/arm64/code-stubs-arm64.cc
+++ b/src/arm64/code-stubs-arm64.cc
@@ -2136,54 +2136,6 @@ void ArgumentsAccessStub::GenerateNewStrict(MacroAssembler* masm) {
 }
 
 
-void RestParamAccessStub::GenerateNew(MacroAssembler* masm) {
-  // x2 : number of parameters (tagged)
-  // x3 : parameters pointer
-  // x4 : rest parameter index (tagged)
-  //
-  // Returns pointer to result object in x0.
-
-  DCHECK(x2.is(ArgumentsAccessNewDescriptor::parameter_count()));
-  DCHECK(x3.is(RestParamAccessDescriptor::parameter_pointer()));
-  DCHECK(x4.is(RestParamAccessDescriptor::rest_parameter_index()));
-
-  // Get the stub arguments from the frame, and make an untagged copy of the
-  // parameter count.
-  Register rest_index_smi = x4;
-  Register param_count_smi = x2;
-  Register params = x3;
-  Register param_count = x13;
-  __ SmiUntag(param_count, param_count_smi);
-
-  // Test if arguments adaptor needed.
-  Register caller_fp = x11;
-  Register caller_ctx = x12;
-  Label runtime;
-  __ Ldr(caller_fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
-  __ Ldr(caller_ctx,
-         MemOperand(caller_fp, StandardFrameConstants::kContextOffset));
-  __ Cmp(caller_ctx, Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
-  __ B(ne, &runtime);
-
-  //   x4   rest_index_smi     index of rest parameter
-  //   x2   param_count_smi    number of parameters passed to function (smi)
-  //   x3   params             pointer to parameters
-  //   x11  caller_fp          caller's frame pointer
-  //   x13  param_count        number of parameters passed to function
-
-  // Patch the argument length and parameters pointer.
-  __ Ldr(param_count_smi,
-         MemOperand(caller_fp, ArgumentsAdaptorFrameConstants::kLengthOffset));
-  __ SmiUntag(param_count, param_count_smi);
-  __ Add(x10, caller_fp, Operand(param_count, LSL, kPointerSizeLog2));
-  __ Add(params, x10, StandardFrameConstants::kCallerSPOffset);
-
-  __ Bind(&runtime);
-  __ Push(param_count_smi, params, rest_index_smi);
-  __ TailCallRuntime(Runtime::kNewRestParam);
-}
-
-
 void RegExpExecStub::Generate(MacroAssembler* masm) {
 #ifdef V8_INTERPRETED_REGEXP
   __ TailCallRuntime(Runtime::kRegExpExec);
@@ -5392,6 +5344,153 @@ void InternalArrayConstructorStub::Generate(MacroAssembler* masm) {
 }
 
 
+void FastNewRestParameterStub::Generate(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- x1 : function
+  //  -- cp : context
+  //  -- fp : frame pointer
+  //  -- lr : return address
+  // -----------------------------------
+  __ AssertFunction(x1);
+
+  // For Ignition we need to skip all possible handler/stub frames until
+  // we reach the JavaScript frame for the function (similar to what the
+  // runtime fallback implementation does). So make x2 point to that
+  // JavaScript frame.
+  {
+    Label loop, loop_entry;
+    __ Mov(x2, fp);
+    __ B(&loop_entry);
+    __ Bind(&loop);
+    __ Ldr(x2, MemOperand(x2, StandardFrameConstants::kCallerFPOffset));
+    __ Bind(&loop_entry);
+    __ Ldr(x3, MemOperand(x2, StandardFrameConstants::kMarkerOffset));
+    __ Cmp(x3, x1);
+    __ B(ne, &loop);
+  }
+
+  // Check if we have rest parameters (only possible if we have an
+  // arguments adaptor frame below the function frame).
+  Label no_rest_parameters;
+  __ Ldr(x2, MemOperand(x2, StandardFrameConstants::kCallerFPOffset));
+  __ Ldr(x3, MemOperand(x2, StandardFrameConstants::kContextOffset));
+  __ Cmp(x3, Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
+  __ B(ne, &no_rest_parameters);
+
+  // Check if the arguments adaptor frame contains more arguments than
+  // specified by the function's internal formal parameter count.
+  Label rest_parameters;
+  __ Ldrsw(x0, UntagSmiMemOperand(
+                   x2, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ Ldr(x1, FieldMemOperand(x1, JSFunction::kSharedFunctionInfoOffset));
+  __ Ldrsw(
+      x1, FieldMemOperand(x1, SharedFunctionInfo::kFormalParameterCountOffset));
+  __ Subs(x0, x0, x1);
+  __ B(gt, &rest_parameters);
+
+  // Return an empty rest parameter array.
+  __ Bind(&no_rest_parameters);
+  {
+    // ----------- S t a t e -------------
+    //  -- cp : context
+    //  -- lr : return address
+    // -----------------------------------
+
+    // Allocate an empty rest parameter array.
+    Label allocate, done_allocate;
+    __ Allocate(JSArray::kSize, x0, x1, x2, &allocate, TAG_OBJECT);
+    __ Bind(&done_allocate);
+
+    // Setup the rest parameter array in x0.
+    __ LoadNativeContextSlot(Context::JS_ARRAY_FAST_ELEMENTS_MAP_INDEX, x1);
+    __ Str(x1, FieldMemOperand(x0, JSArray::kMapOffset));
+    __ LoadRoot(x1, Heap::kEmptyFixedArrayRootIndex);
+    __ Str(x1, FieldMemOperand(x0, JSArray::kPropertiesOffset));
+    __ Str(x1, FieldMemOperand(x0, JSArray::kElementsOffset));
+    __ Mov(x1, Smi::FromInt(0));
+    __ Str(x1, FieldMemOperand(x0, JSArray::kLengthOffset));
+    STATIC_ASSERT(JSArray::kSize == 4 * kPointerSize);
+    __ Ret();
+
+    // Fall back to %AllocateInNewSpace.
+    __ Bind(&allocate);
+    {
+      FrameScope scope(masm, StackFrame::INTERNAL);
+      __ Push(Smi::FromInt(JSArray::kSize));
+      __ CallRuntime(Runtime::kAllocateInNewSpace);
+    }
+    __ B(&done_allocate);
+  }
+
+  __ Bind(&rest_parameters);
+  {
+    // Compute the pointer to the first rest parameter (skippping the receiver).
+    __ Add(x2, x2, Operand(x0, LSL, kPointerSizeLog2));
+    __ Add(x2, x2, StandardFrameConstants::kCallerSPOffset - 1 * kPointerSize);
+
+    // ----------- S t a t e -------------
+    //  -- cp : context
+    //  -- x0 : number of rest parameters
+    //  -- x2 : pointer to first rest parameters
+    //  -- lr : return address
+    // -----------------------------------
+
+    // Allocate space for the rest parameter array plus the backing store.
+    Label allocate, done_allocate;
+    __ Mov(x1, JSArray::kSize + FixedArray::kHeaderSize);
+    __ Add(x1, x1, Operand(x0, LSL, kPointerSizeLog2));
+    __ Allocate(x1, x3, x4, x5, &allocate, TAG_OBJECT);
+    __ Bind(&done_allocate);
+
+    // Compute arguments.length in x6.
+    __ SmiTag(x6, x0);
+
+    // Setup the elements array in x3.
+    __ LoadRoot(x1, Heap::kFixedArrayMapRootIndex);
+    __ Str(x1, FieldMemOperand(x3, FixedArray::kMapOffset));
+    __ Str(x6, FieldMemOperand(x3, FixedArray::kLengthOffset));
+    __ Add(x4, x3, FixedArray::kHeaderSize);
+    {
+      Label loop, done_loop;
+      __ Add(x0, x4, Operand(x0, LSL, kPointerSizeLog2));
+      __ Bind(&loop);
+      __ Cmp(x4, x0);
+      __ B(eq, &done_loop);
+      __ Ldr(x5, MemOperand(x2, 0 * kPointerSize));
+      __ Str(x5, FieldMemOperand(x4, 0 * kPointerSize));
+      __ Sub(x2, x2, Operand(1 * kPointerSize));
+      __ Add(x4, x4, Operand(1 * kPointerSize));
+      __ B(&loop);
+      __ Bind(&done_loop);
+    }
+
+    // Setup the rest parameter array in x0.
+    __ LoadNativeContextSlot(Context::JS_ARRAY_FAST_ELEMENTS_MAP_INDEX, x1);
+    __ Str(x1, FieldMemOperand(x0, JSArray::kMapOffset));
+    __ LoadRoot(x1, Heap::kEmptyFixedArrayRootIndex);
+    __ Str(x1, FieldMemOperand(x0, JSArray::kPropertiesOffset));
+    __ Str(x3, FieldMemOperand(x0, JSArray::kElementsOffset));
+    __ Str(x6, FieldMemOperand(x0, JSArray::kLengthOffset));
+    STATIC_ASSERT(JSArray::kSize == 4 * kPointerSize);
+    __ Ret();
+
+    // Fall back to %AllocateInNewSpace.
+    __ Bind(&allocate);
+    {
+      FrameScope scope(masm, StackFrame::INTERNAL);
+      __ SmiTag(x0);
+      __ SmiTag(x1);
+      __ Push(x0, x2, x1);
+      __ CallRuntime(Runtime::kAllocateInNewSpace);
+      __ Mov(x3, x0);
+      __ Pop(x2, x0);
+      __ SmiUntag(x0);
+    }
+    __ B(&done_allocate);
+  }
+}
+
+
 void LoadGlobalViaContextStub::Generate(MacroAssembler* masm) {
   Register context = cp;
   Register result = x0;